How is a magnetic field generated?
a. an isolated magnetic pole
b. gravity
c. charged particles that do not move
d. moving electric charges
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8. why do radio telescopes convert radio waves (analog signals) to electrical (digital) signals for analysis? (hint: what did the article say about the advantages of digital signals? )

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.

What are the similarities & differences between a thermistor and a light dependent resistor in physics?